Exterior Wall Finishing
BY FRANK GEHR · FEBRUARY 21, 2014
The exterior wall covering is the single most dominant feature of a home’s outer appearance; its color and texture are the first things noticed by anyone approaching the house. Good design calls for simple lines, common sense in the selection of materials, harmonious textures and colors, plus good proportions and scale. A hash of materials such as a bit of stone here, some brick over there, with shingles and clapboards and stucco all mixed above, will give the impression that the house is desperately trying to trick observers into liking some detail, and more often than not will ruin a dwelling’s appearance.
Beyond its cosmetic nature, the exterior wall covering also acts as the final protective layer between a home’s occupants and the great outdoors. More specifically, it is this outer “sandwich” layer that, along with its interior counterpart, envelops whatever insulation is chosen to help protect family members from temperature extremes, and minimizes the need to import or purchase additional energy required for comfort. Attached to the frame or masonry walls can be wood siding in various forms, brick, stone, stucco, aluminum and vinyl sidings, shingles of metal, asphalt, or plastic, and many other lesser-used siding materials.
When selecting the material for your home’s siding, consider how the following characteristics stack up against those materials in the running.
– Cost of materials
– Cost of installation labor, ease of handling by size, weight, and shape
– Resistance to natural weathering, chemical attack, and atmospheric pollution
– Resistance to scratching and impact
– Appearance of color and texture
– Dimensional changes resulting from temperature and moisture
– Resistance to moisture penetration
– Sound insulation and absorption
– Strength under conditions of compression, bending, shear, and tension to carry applied loads and resist the pressure of wind
– Adaptability to future expansions and other modifications
– Susceptibility to insect damage
ALUMINUM AND VINYL SIDING
Aluminum and vinyl sidings are available in many different colors and shades, textures, and forms for both horizontal and vertical installation. When used alone or in combination with each other to cover exterior wood surfaces, they’ll practically eliminate the need for future wood refinishing and painting chores. These sidings can also help provide additional thermal and sound insulation when installed over polystyrene or similar backer boards.
Indeed, recent manufacturing innovations enable many sidings to have wood-grain finishes or textures that look, and often feel, just like painted wood, smooth “clear” cedar, cedar shakes, weathered cedar, teak, or fir, roughsawn barnboard, and other varieties. All feature sturdy locking mechanisms so that individual panels will resist wind and weather.
For example, horizontal siding panels generally interlock where they overlap, as do the panels of double 4-inch clapboard, double 5-inch, and triple 3-inch, plus double 41⁄2-inch wood-grain shiplap.
Aluminum siding is a low-maintenance exterior wall covering that won’t rust in the ordinary sense. Its baked-on finish lasts for 20 to 40 years, depending on the grade purchased. Aluminum siding won’t rot, split, warp, or crack. It’s manufactured in a wide variety of colors and shades from light pastel tints to whites to deep rich tones, and comes in numerous textures and finishes—some resembling wood siding. The difference in price and insulating qualities is small.
Vinyl siding is another popular low-maintenance wall covering that’s manufactured essentially in the same forms as aluminum siding. As with aluminum siding, vinyl can be backed with a polystyrene or other board reinforcement both to give the siding a strong base and an insulating R-value (especially when also backed with several layers of house wrap). A major advantage to vinyl siding is that the color is molded throughout the entire thickness of the material, so a scratch will do little damage.
Neither will vinyl siding dent; it’s resilient nature allows it to spring back into shape after all but the most violent blows. Look for a vinyl siding that’s a double thick .088-inch rolled-over nail hem design that increases wind resistance and stiffens the panel. Such a design may withstand wind load pressures up to 180 miles per hour when installed with nails and up to 235 miles per hour with staples.
This siding panel should feature a true .044-inch thickness for outstanding strength and durability. Most modern vinyl sidings have onestep panel locking systems for secure installation and perfect horizontal or vertical alignment. Too, the color goes clear through the vinyl, so scratches won’t show, and a special sunshield technology is often used to protect the surface from harmful sun ultraviolet rays.
Drawbacks to vinyl are that it’s inclined to buckle or ripple if not installed exactly correct, and it’s not as readily adaptable as aluminum is to cover unusual or unique exposed wood trim.
No matter which type of aluminum or vinyl siding is selected, make sure the contractor correctly applies caulking around the doors, windows, and corners—wherever the siding forms a seam across its grain or meets with different building materials. The contractor should also use aluminum nails for fastening the siding materials to exterior walls. Aluminum nails won’t rust and form unsightly streaks.
To permit the latter method, a separate outer foundation must be constructed to support the brick or stone walls. In either case, there must also be a space between the masonry and interior wall surfaces, and this space should contain proper insulation and a vapor barrier.
The first choice (of moving the walls inward to accommodate the thickness of bricks or stones) should require no change in the home’s roof structure, particularly to the overhang and exterior trim. The second choice (of building out) might, however, require alterations in these areas to accommodate the wider dimensions of the outer limits to the exterior walls.
Brick makes a very attractive exterior, with numerous colors and textures available. All of one color can be used, or a mottled effect can be had by using many different shades or colors in the same surface. The best way to arrive at what you’d like is to take a drive through neighborhoods that have plenty of brick homes. A few color snapshots of what most appeals to you can be handed to your contractor, who will be able to tell you where those bricks can be purchased or ordered.
It should be noted that most bricks are manufactured with holes in their centers. When mortar is applied to the bricks, some of it fills those holes and provides additional bonding strength when dried. If the top of any bricks need be exposed, enough solid bricks without holes should be ordered along with the others. The same principle applies to textured bricks where typically only one side—the exposed side—is textured. When bricks are needed to have a textured surface exposed on two or three or four surfaces, special bricks that are textured all around will have to be ordered. Remember that a brick wall will cover a structure, but won’t support it. The stud wall provides the support. Instead, metal anchors tie the brick wall to the frame wall.
Make sure the contract specifies that the masons must finish the job by cleaning the brick with the brick manufacturer’s cleaning solvent. Muriatic acid can stain brick.
Stone also makes an attractive exterior that’s durable and practically maintenance-free. It has most of the advantages and disadvantages of brick.
Stonework is usually more costly than brick. In general, stones cut with rectangular corners are more commonly used for covering exterior walls. Rubble or fieldstones having irregular shapes and no corners can be employed in a feature wall for dramatic effect to create a rustic appearance.
Openings in Masonry Exterior Wall Coverings
Due to the weight of brick and stone, door and window openings require special supports to hold the brick or stone securely in place above those openings. There are three common ways to provide such support: with steel lintels, curved brick arches, and flat brick arches.
The steel lintel is the simplest to install. It consists of “angle iron” of appropriate length that overlaps the top of the door or window opening on either side, so the weight of the brick or stone above the opening can be transferred to and distributed throughout the adjacent masonry structure. The curved brick arch is constructed of standard size and shape bricks or stones to span the opening, and the flat brick arch is formed with specially cut bricks.
WOOD SHINGLES AND SHAKES
Wood shingles and shakes are usually made of cedar, but can be made of redwood or cypress. Cedar shingles or shakes are used as siding when a homebuyer wants an eye-catching rustic appeal to the home and a “warm” siding that’s naturally resistant to decay and is an excellent insulation. Cedar has a golden brown color when new, that gradually darkens with age, and finally weathers into an attractive silver-gray, depending on the climate (the amount of sunlight and humidity) it’s located in.
The difference between shingles and shakes is that both sides of shingles are sawn smooth, while shakes have at least one rough-textured side created by splitting it from the mother log. These are the same shingles and shakes that are also used for roofing.
While cedar, redwood, and cypress shingles and shakes can be installed in some climates without being coated with preservatives, weathering everywhere is best controlled by applying recommended weatherproofings every five or six years. Pressure-treated Southern yellow pine is also an acceptable substitute, when available.
The best wood shingles and shakes are free from knots and pockets of pitch. You can tell the difference between the best and lower grades by the wood grain—it should be regular and clear with few or no defects.
Drawbacks to wood shingles and shakes include their cost: they’re expensive and time-consuming to apply. Unless you opt for shingles and shakes prefabricated into 8-foot panels, each shingle or shake must be hand nailed into place, one at a time. They’re also susceptible to fire.
Only nonrusting nails that provide sturdy holding power should be used to fasten wood shingles and shakes to the walls. Common nails won’t hold well enough and will rust and streak the siding.
Molded “Cedar” Shingles
Molded shingles that look like wood are available in vinyl, polypropylene, and other plastic materials. Models include both halfround shingle panels and “full perfection” shingle panels. While offering the look of real wood, these panels are practically free from splitting, warping, cupping, twisting, fading, or streaking. They also need no painting or repetitive surface protection. The panels are typically about 0.100-inch thick with ribbed backer components that add structural stability. These molded shingles hold up well in rainy, windy, and coastal climate locations, especially when backed with reflective building foil.
SOLID WOOD SIDING
Almost any type of wood can be used for solid plank siding, including such species as cedar, redwood, fir, cypress, pine, spruce, and hemlock. Redwood siding in particular is very durable. It resists
deterioration from the weather and from insects. Unpainted redwood surfaces will darken season by season to a deep grayish brown.
Solid wood siding comes in many styles for horizontal and vertical applications, including beveled, dropped, and beaded planks for horizontal sidings, and V-groove, tongue-and-groove, board-and batten, and channel vertical sidings.
Beveled horizontal wood siding is probably the most popular of all solid wood exterior wall coverings because it so nicely complements most styles of architecture. It consists of long boards, available in varying thicknesses and widths having beveled edges and tapered to exaggerate the deep, long horizontal shadow lines at the lower edges of the planks that help provide character to a dwelling’s appearance. The individual boards are usually installed over a sheathing and building paper, nailed through them to the exterior wall studs. Corners are covered with either metal corner pieces or wood corner boards. The thickness of the corner boards should be at least 1 inch to provide a substantial caulking base.
The old-fashioned clapboard siding that once covered (and still covers) many a home consists of wood planks of uniform thicknesses.
Plywood siding can be supplied in many varieties of wood and patterns at varying costs. Check with your local suppliers to see samples. Only exterior types of plywood should be considered those having their layers of veneer bonded together with a tough waterproof glue.
Plywood panels are manufactured in 4-foot widths and 8- to 12-foot lengths that, due to their size and ease of installation, help hold down labor costs. If you plan to use plywood siding, match the correct length panels to the requirements of your home to have as few horizontal joints as possible, because they’ll detract from the overall appearance and can be a source of water and moisture leaks if not correctly installed.
Plywood panel vertical application.
Because of its strength, plywood siding is sometimes applied directly to the wall studs, without the use of an underlayment sheathing.
Hardboard sidings are manufactured panels consisting mostly of wood products. They come in more finishes and textures than ply-woods, but are not as strong.
On the positive side, factory-made hardboard sidings are free from natural defects. Their panels are stiffer and less likely to warp or bend. Both the texture and depth of wood are presented in authentic-looking wood grains and grooves. The better hardboard or wood fiber sidings are over 50 percent denser than real wood planking and won’t crack, split, check, or delaminate. They can also be purchased primed ready for custom finishing in multiple lap sheets that are easy to install without having to nail narrow individual boards.
Remember that even factory-finished hardboard sidings will probably have to be refinished eventually.
Stucco is that plasterlike material so popular with English Tudor construction. It’s an excellent exterior finish, having a long life span and needing very little maintenance. It’s really a version of Portland cement that’s troweled on like plaster to either masonry or frame walls, with no seams or joints. It’s usually made in white, but can be colored with any paint manufactured for application over masonry. There’s also a wide selection of pigments available that can be added to the stucco mix. If deeper hues are desired, the stucco can be painted in the same fashion as concrete block.
Stucco can be applied as a finish coat to both existing houses and new construction. It can be finished to give a number of interesting textures to conform with traditional or modern architectural styling.
Three coats with a total thickness of about 3⁄4 inch are generally recommended. When stucco is applied over the sheathing of a wood-framed house, a layer of stucco wrap can be placed over the sheathing. Stucco wrap is a type of engineered construction fabric or membrane (also see house wrap, in the section on Vapor Barriers). Stucco wrap creates a drainage path for water and moisture to escape. It will take water and moisture that may enter the walls from the interior spaces and around windows, doors and other joints, and channel it outside. It thus helps prevent water and moisture from harming the sheathing, framing and insulation—which can cause expansion and contraction, leading to stucco fractures and cracking.
Stucco wrap is also good at managing the hydration process of the stucco material during the curing. The scratch coat will not absorb water from the other stucco coats because, again, the stucco wrap channels the water and moisture toward the outside. Because the scratch coat will not absorb extra water, it won’t expand and contract much during curing. The result is a dramatic reduction of cracking in the scratch coat. This helps create a strong, stable stucco, with each layer drying at a similar rate, front to back. A white stucco wrap is often preferred because it won’t absorb much heat from the sun, and the cooler surface further extends the stucco drying time, so cracking is even less likely. Less stucco cracks makes a more solid energy efficient exterior wall.
To reinforce why vapor and air-infiltration barriers are needed, it’s been estimated that the typical home can have close to a half mile of undesirable cracks and crevices in its outer shell that can let out warm air during winter, and cooled air during summer.
In addition, unwanted moisture that enters walls can lead to mold, mildew, and rot. Wall moisture originating from within a building can sometimes be more damaging than outside moisture penetration.
Daily activities within a household such as showering, cooking, washing clothes and dishes, and even breathing produce moisture vapor that needs to escape. Again, without proper vapor barriers, as the temperature increases within a home, inside water vapor is transmitted into walls, where it condenses. This condensation results in a wetting of structural materials and in a loss of the insulating qualities of exterior walls. It also gives rise to such serious problems as chemical, physical, or biological deterioration of the wall materials, and promotes corrosion of metal, spalling of brick, and rotting of timbers.
House wrap—an engineered construction fabric or membrane—can be used on the outside of a wall, against some wall sheathings, to protect the sheathing from water and moisture. If properly installed, exterior house wrap placed over certain exterior sheathings can improve comfort, energy efficiency, and will protect against moisture and water damage.
Installed over wood or certain insulation sheathings, and under siding or other exterior coverings, house wrap provides a protective barrier which helps seal against leaks and drafts (air infiltration).
On the other hand, as some manufacturers of rigid sheathing panels point out, if their panels are properly installed, there should be no air leaks through cracks or seams (or very minimal air leaks). If that’s true, they say, then additional installation of house wrap over those panels may actually create harmful conditions by trapping eventual residues of wood starches from siding materials and from cleaning detergents that may become trapped within the house wrap fabric (thus plugging the fabric meshing so it can no longer breathe).
In many other situations, though, house wrap works hand-in-hand with insulation. Using a clothing analogy, the home’s insulation traps air in tiny pockets (like a thick cable-knit wool sweater does) to slow the transfer of heat, while house wrap functions like a Goretex windbreaker does, when layered over the wool sweater. Where properly used, house wrap should thus cover or seal:
– Gaps between sheathing pieces or panels
– Joints between the sole plate and sub floor along exterior walls
– Gaps in drywall or plaster board and top and bottom wall plates
– Where framing members meet in an outside intersection and form a crack
– Around window and door frames
– Electrical and plumbing penetrations through top and bottom wall plates.
An effective house wrap design resists tears in all directions, stands up to windy conditions, with good tensile strength. Also, it should only enable condensation to evaporate or drain away from the house sheathing. Around windows and doors, house wrap can be used in the sill rough openings before a window or door is installed. A straight flash wrap is available for straight heads and jambs of windows and doors to effectively seal gaps. House wrap tape is manufactured for taping house wrap seams, tears, and openings such as holes and open spaces around electrical boxes, venting ducts, and similar construction components and materials. Before deciding on a vapor/air infiltration system for your home, at least be aware of the various strategies, and discuss them with your builder.
Make sure the particular house wrap or rigid panels are compatible with the planned siding. For example, certain cedar and other wood siding may need special add-ons to enable the siding to breathe from both sides. Consider that many new products are in the process of coming to market, so carefully research their pros and cons, then consider your house style and the weather conditions in your locale. It’s far less expensive, and a much simpler process, to design the barrier system for installation during construction—than to try to upgrade or change systems at a later date.
Insulating batts in the exterior walls should have a vapor barrier backing such as treated Kraft paper with the vapor barrier on or toward the living-area side. If blown insulation or unfaced insulation is chosen, aluminum foil–backed drywall can be used, or friction fit or other types of insulation can be applied after polyethylene sheet material is stapled or nailed to the interior of the wall studs and ceiling joists. The polyethylene film should not be less than 3 mils thick.
Underneath the sheathing and exterior wall covering, between the studs, one of the following types of insulation will generally be used:
– Batts or blankets—these are prepared thicknesses of expanded glass fiber, mineral fiber, or organic fiber that are placed in the walls between the studs. They should be faced (having a vapor barrier on one side) in order to hold their form well.
– Blown or poured—this is composed of loose expanded mineral or organic fibers that are placed or blown into frame spaces. They’re more useful for insulating existing buildings when it would be impractical to completely remove the inner or outer wall sheathings. On the down side, blown or poured insulation may eventually settle and lose some of its insulating value.
If you choose to use vinyl or aluminum siding, remember that polystyrene and similar backer boards can be used behind the siding panels to provide extra insulation as well as added strength.
Or, this leads us to another recent product development that’s become especially pertinent in this time of rising fuel costs, that of exterior rigid foam insulation. Exterior rigid foam insulation is made of extruded polystyrene or similar material that has an R-value of about R-5 per inch of product thickness. It contains literally hundreds of millions of densely packed air cells. Since air is one of nature’s most effective insulators, the sheer volume of this compressed trapped air gives this insulation exceptional thermal performance. It also prevents air infiltration and resists moisture penetration.
In some cases, these panels can be installed over exterior sheathing (as long as the total vapor/air-infiltration barrier system isn’t over engineered to prevent at least some healthy “breathing”). For example, a cost-effective way to achieve a R-19 wall system is to install 1-inch extruded polystyrene foam insulation to the exterior sheathing of a 2″ by 4″ wall cavity filled with R-13 fiberglass insulation. Exterior sheathing, siding, and interior drywall typically provide an R-value of R-1. A 2″ by 6″ wall cavity filled with fiberglass insulation will give an even greater R-value. The exterior layer of foam insulation will also help reduce road noise, will help prevent air infiltration, and will increase comfort through less radiant heat loss because the entire mass of the wall structure is covered.
Again, when dealing with barrier products, it’s important to have a strategy that manufacturers and builders will somewhat agree upon, so the combination of several different products will work in your favor and will not inadvertently cause moisture or air circulation/breathing problems.
ENERGY-SAVING OUTDOOR PAINT
Many of these paints use microscopic insulating ceramic spheres in their composition to help create a sturdy reflective, radiant barrier to ward off the sun’s heat, especially in white and lighter shades of color. They also protect against moisture, and provide an excellent choice when sealing joints and narrow cracks and spaces around vents, trim, and fastening devices.
Paints with insulating ceramics resist stains, corrosion, mold and mildew, and can be scrubbed clean, help deaden sound, and are effective in hot and cold climates. They can be applied with brush or roller, and are simple to use for touch-up tasks.
Request that the siding contractor provide waterproof maintenance-free hoods in colors that match your siding for dryer and other intake/exhausts.
Color-matching mounting plates for mailboxes, hose reels, electrical outlets, coach lamps, and other lights and fixtures are usually available in vinyl and plastic. While these may sound like “small” details, they can all contribute to a handsome exterior—without ungainly distractions caused by mismatching hardware.
ILLUMINATED HOUSE NUMBERS
Many police, paramedic, or fire department personnel will tell you about the amount of time lost nights trying to locate a house for an emergency call when the home’s address numbers are not readily identifiable. Consider asking the contractor to quote on a decorative low-voltage address number fixture.
They’re inexpensive to operate and easy to read, day or night. They’re made from maintenance-free vinyl or plastic products that also come in colors to match the siding.
There’s something old-fashioned about a good set of fabric awnings. Maybe it’s the additional level of privacy they provide when installed over windows, doors, decks or patios. Or maybe it’s the additional color they add, or their ability to be adjustable. They also protect—to a certain extent—against rain, wind, and sunlight. In fact, canvas and other fabric awnings block out or absorb up to 99 percent of the sun’s harmful ultraviolet rays, and can reduce the amount of sunlight and glare passing through windows by as much as 94 percent. Awnings can thus reduce heat gain through windows—up to 77 percent on eastern and western windows.
They’ll also protect indoor furnishings such as carpeting, curtains, and furniture from sunlight fading, while keeping the inside environment cooler, with lower air-conditioning costs. On the down side, awnings eventually wear out. They’ll need maintenance and eventual replacement as well as routinely being put up and taken down, depending on seasonal weather patterns; this could raise safety issues, especially with second-story installations. One possible answer to durability concerns is that of rigid awnings, awnings constructed of aluminum, plastic, or composite materials.
Especially where snow and ice are not issues, rigid awnings can provide many of the advantages of their fabric cousins and can be left in place year-round.
There are many types and styles of awnings. Consider these features if you decide to investigate their use on your home:
– Do the units require minimal maintenance?
– Are they self-storing?
– Is the awning material resistant to ultraviolet light, mildew, and water?
– Is the awning operated with a manual crank, or is motorized?
– Is it an under-the-eave mount, or flat-wall mounted?
– Does it have stainless steel or other hardware that will not rust or deteriorate?
– Are there oil-impregnated bearings, so there’s no need for lubrication?
– Do the units have strong, lightweight, rustproof frames with a baked enamel finish?
Ventilation gables can be critical to planning for sufficient air movement into an attic or other “open” spaces beneath upper reaches of the roof. Air movement will help remove dampness and hot air, thus helping the insulation and lumber there. Some manufacturers offer copolymer construction gable vents with ultraviolet-stabilized colors molded throughout, and fully screened for insect, bat, and bird protection. These units can be installed on all types of exteriors, including wood, vinyl, aluminum, stucco, hardboard, stone, and brick.
SIDING GENERAL CONSIDERATIONS
– It’s a good idea to view the work of masons the builder is planning to use on your siding. Ask to see recent completed projects whether they’re in brick, stone, or stucco.
– Decide if you want a matching stoner brick mailbox or light posts on either side of the driveway or walk before masonry siding is applied.
– It should be stated in the contract that the builder should see that only OSHA-compliant scaffolding is used for all elevated work.
– The exterior siding contractor should also quote on any wrought iron railings needed.
– The exterior siding contractor should figure in trim around the doors, windows, and at the corners of the home. Flashing must be installed at the head and sill of all door and window openings. Trim should be securely fastened and well caulked wherever needed. Request tinted caulk that matches the siding color.
– House wrap fastened over plywood will help keep out wind and water. Flashing at the base of the wrap will help carry off water from the wall, and weep holes between bricks, stones, or in the vinyl or aluminum siding will allow water to escape.
– Wood siding should clear the ground surface for less chance of wood-boring insect damage and decay from moisture.
– The agreement should specify if any brick, stone, shingle, or shake siding must be treated with water repellant after the siding has had sufficient time to “dry out.” For example, the contractor should not paint right after installation of wood, but should wait until the wood has a chance to dry. If it shrinks after being coated, that will leave unpainted strips of wood where the pieces overlap.
– No matter which siding you plan, ask the contractor to handpick the best material for the front and back of the home, where appearance is most important.
– See that only exterior, nonrusting fasteners are used in all siding applications.
– Nails must be driven flush or countersunk.
– All laps of siding must be parallel, and all joints should be staggered between courses.
POINTS TO PONDER